The Living Textbook has recently published materials that explore how randomized trials can be designed to promote both internal and external validity. The new contributions, from Drs. Merrick Zwarenstein, Ahmed Al-Jaishi, and Amit Garg, explain that consideration of the trial’s intention, whether pragmatic or explanatory, is the key to designing a trial that successfully answers its primary research question. While there is a contrast between pragmatic and explanatory intentions, there is not a dichotomy. Instead, trials will vary across the spectrum of design decisions leaning toward choices that match the trial’s purpose. The PRECIS-2 tool can help investigators design their trial to align with its intention. The authors illustrate these points in a new Living Textbook section, PRECIS-2 Case Study, which contrasts the design decisions made for two trials in a renal dialysis setting.
“The purpose should be decided before embarking on designing a trial, and each element of the trial design should be aligned to the chosen purpose.”– Zwarenstein et al. 2021
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